It was their work on the world's thinnest material that was recognised by the Nobel committee in 2010 for "for groundbreaking experiments regarding the two-dimensional material graphene".

Graphene is a form of carbon. It is a flat layer of carbon atoms tightly packed into a two-dimensional honeycomb arrangement.

Because it is so thin, it is also practically transparent. As a conductor of electricity, it performs as well as copper; and as a conductor of heat, it outperforms all other known materials.

The unusual electronic, mechanical and chemical properties of graphene at the molecular scale promise ultra-fast transistors for electronics.

Some scientists have predicted that graphene could one day replace silicon - which is the current material of choice for transistors.

It could also yield incredibly strong, flexible and stable materials and find applications in transparent touch screens or solar cells.

Cracking the code

Another Nobel laureate to be recognised with a knighthood is Venki Ramakrishnan, a biologist based at the Medical Research Council's Molecular Biology Laboratories in Cambridge, UK.

I am delighted and humbled by this honourProf Bob Watson

In 2009, he and two other scientists were the recipients of the Nobel Prize in Chemistry for their work on the structure and function of the ribosome - the cell's protein factory.

The ribosome translates genetic code into proteins, which are the building blocks of all living organisms.

At the time, commentators said India-born Prof Ramakrishnan's and the other scientists' work solved an important part of the the problem posed by Francis Crick and James Watson when they discovered the now iconic double helix DNA structure - how does this code become a living thing?

Prof Bob Watson, Defra's chief scientific adviser, has also received a knighthood and he told BBC News that he was delighted to receive the honour.

"I am delighted and humbled by this honour, which implicitly recognises the value of scientific knowledge in national and international environmental policy formulation," he said.

He has been Defra's top scientist since 2007, and his position means he is ultimately responsible for the broad range of science that falls under the department's remit, such as climate change and bovine TB.

On the Defra website, his main role is described as providing "ministers with the best possible scientific advice and build on existing measures to ensure that science and technology are used to inform policy".

Before joining Defra, US-born Prof Watson worked as chief scientist at the World Bank. He also held senior positions at Nasa, the White House, as well as being chairman of the Intergovernmental Panel on Climate Change (IPCC), the UN-sponsored scientific body.